The command:
show log vpn ipsec
Produces no output under VyOS 1.2.2
Now that StrongSWAN uses charon instead of pluto for IKEv1,IKEv2, the show log function greps for the wrong daemon:
cat /opt/vyatta/share/vyatta-op/templates/show/log/vpn/ipsec/node.def help: Show log for IPSEC run: cat $(printf "%s\n" /var/log/messages* | sort -nr) | grep -e pluto